1. Field of the Invention
This invention relates to a sputtering apparatus which produces thin films for thin film devices or the like with use of a laser beam.
2. Description of the Prior Art
FIG. 3 shows a conventional sputtering apparatus utilizing a laser beam, the construction of which is as described by S. Komura et al. in "Japanese Journal of Applied Physics" (p. 23, vol. 27 (1988)). The sputtering apparatus comprises a vacuum chamber 14 in which a target 15 and a substrate stage 16 are disposed facing each other. A substrate 17 is placed on the substrate stage 16. A laser beam 18, which is the second-order harmonic (which is visible light with a wavelength of 532 nm) of the laser beam emitted from a Q-switch YAG laser, is converged by an optical system 19 and directed through a vacuum sealing window 20 provided on the vacuum chamber 14, and then projected onto the target 15. Upon receiving the laser beam 18, the material of the target 15 is sputtered out of the surface thereof and then deposited on the substrate 17 to form a thin layer thereon.
In a sputtering apparatus with the above configuration, however, since the intensity of the laser light varies from one portion to another on the surface of the target 15, the thickness of the resultant thin layer becomes uneven. Moreover, in the case where the film-forming process is repeated over and over for a long time, the portion of the target 15 onto which the laser beam with a greater intensity is always projected tends to be sputtered away from the surface thereof to a greater degree, as compared with the other portion, resulting in a recess with a substantial depth on the target 15. When the laser beam is diagonally directed onto the target 15 with such a recess, the material in the recess cannot receive a sufficient amount of laser light, which further causes unevenness in the resultant thin film.
In order to form a thin film with a uniform thickness, many conventional sputtering apparatuses adopt the arrangement in which the substrate is moved so as to receive the sputtered material with a uniform thickness thereon. This requires a complicated mechanism, and still cannot solve the above-mentioned problem of the deformation of the surface of the target caused by the repeated film-forming processes.